Mars Trigger MP5 Complete Lower System (Super Safety)

The Mars Trigger MP5 Complete Lower System is the least fiddly way to put a forced reset trigger in a roller-delayed 9mm. Instead of selling you a trip and a selector and leaving you to source an AR fire control group and a compatible lower, Mars ships a complete drop-in MP5 lower with the AR FCG and a Hoffman 3-position Super Safety selector already installed and timed. You pull your factory trigger housing, push two pins, and run. Every forced reset design works the same way: the bolt carrier's rearward travel mechanically forces the trigger back into reset after each shot and holds it until the action returns to battery, so each press fires one round. Mars builds the system around the Super Safety, which is a selector and not a trigger; the selector's third position is what enables forced reset behavior.

Mars sells the lower per host rather than as a one-size unit, which is the right call on a platform where grip-frame geometry and selector cuts differ between makers. The lineup covers HK SP5 and SP5K, PTR 9 and 9K, and the AP5 and AP5-K family (which also covers Zenith ZF5/ZF5-K and the MAC5 lineage), at a flat $599.95. The slip/trip is hardened D2 tool steel and the internals are built to absorb the higher cyclic abuse a forced reset puts on a fire control group.

At $599.95 it costs about the same as a Rare Breed FRT-RD3 but removes the parts hunting and timing work, which is the entire pitch. The trade is that you are buying a whole lower rather than a drop-in cassette, so it is a per-gun purchase rather than a part you can move between hosts. Treat legal status as something to confirm before ordering; forced reset triggers are federally lawful after the May 2025 DOJ settlement but are banned or restricted in roughly fifteen states.